pw_tokenizer: Use uint64_t for calculation

Some compilers treat the intermediate calculation as multiplication
and addition overflow when UBSanitizer is enabled because the
arithmetic logic is using uint32_t as containers that get overflow with
the multiplication and addition.
Since the token is compile time evaluated, using uint64_t as containers
won't make any differences but can safely pet the compilers.

Change-Id: I4efb95f4eb361aab02dcda37002ebe52380e91b2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/232851
Presubmit-Verified: CQ Bot Account <[email protected]>
Reviewed-by: Aaron Silman <[email protected]>
Lint: Lint 🤖 <[email protected]>
Reviewed-by: Wyatt Hepler <[email protected]>
Commit-Queue: Hungyen Weng <[email protected]>